Controller area network (can) device and method for operating a can device

ABSTRACT

Embodiments of a method, a device and a computer-readable storage medium are disclosed. In an embodiment, a method for operating a Controller Area Network (CAN) device involves in response to receiving bits of an arbitration field of a CAN data frame at the CAN device, selecting a timing engine from a plurality of timing engines and sampling subsequent bits of the CAN data frame using the selected timing engine. The timing engines have different sample clock frequencies.

BACKGROUND

Controller area network (CAN) bus is a message-based communications busprotocol that is often used within automobiles. The CAN bus protocol isused to enable communications between various electronic control units(ECUs), such as an engine control module (ECM), a power train controlmodule (PCM), airbags, antilock brakes, cruise control, electric powersteering, audio systems, windows, doors, mirror adjustment, battery andrecharging systems for hybrid/electric cars, and many more. The datalink layer of the CAN protocol is standardized as InternationalStandards Organization (ISO) 11898-1. The standardized CAN data linklayer protocol is in the process of being extended to provide higherdata rates. The extended protocol, referred to as CAN Flexible Data-Rateor “CAN FD,” is moving towards standardization in the form of an updateof the existing ISO 11898-1 standard. The CAN bus protocol does not havededicated clock lines between communicating devices and receivingdevices. Consequently, CAN devices communicate without a common clocksignal.

SUMMARY

Embodiments of a method, a device and a computer-readable storage mediumare disclosed. In an embodiment, a method for operating a CAN deviceinvolves in response to receiving bits of an arbitration field of a CANdata frame at the CAN device, selecting a timing engine from timingengines and sampling subsequent bits of the CAN data frame using theselected timing engine. The timing engines have different sample clockfrequencies.

In an embodiment, the method further comprises modifying at least someof sampled subsequent bits of the CAN data frame using the sample clockfrequency of the selected timing engine.

In an embodiment, the CAN data frame further comprises a data field, andsampling the subsequent bits of the CAN data frame using the selectedtiming engine comprises sampling bits of the data field of the CAN dataframe using the selected timing engine.

In an embodiment, modifying the at least some of the sampled subsequentbits of the CAN data frame comprises modifying at least some of thesampled bits of the data field using the sample clock frequency of theselected timing engine.

In an embodiment, selecting a timing engine comprises selecting a besttiming engine and at least one candidate timing engine.

In an embodiment, the best timing engine and the at least one candidatetiming engine sample the same data from the received bits of thearbitration field.

In an embodiment, the best timing engine exhibits the lowest timingerror among the best timing engine and the at least one candidate timingengine.

In an embodiment, the method further comprises evaluating the besttiming engine and the at least one candidate timing engine based on thesubsequent bits of the CAN data frame.

In an embodiment, evaluating the best timing engine and the at least onecandidate timing engine based on the subsequent bits of the CAN dataframe comprises selecting a second timing engine with the lowest timingerror among the best timing engine and the at least one candidate timingengine. The method further comprises sampling further bits of the CANdata frame that are received after the subsequent bits of the CAN dataframe using the second timing engine.

In an embodiment, a CAN device includes timing engines and a timingengine resolver configured to, in response to receiving bits of anarbitration field of a CAN data frame at the CAN device, select a timingengine from the plurality of timing engines. The timing engines havedifferent sample clock frequencies. The selected timing engine samplessubsequent bits of the CAN data frame.

In an embodiment, the CAN device further includes a bit manipulationmodule configured to modify at least some of sampled subsequent bits ofthe CAN data frame using the sample clock frequency of the selectedtiming engine.

In an embodiment, the CAN data frame further comprises a data field, andthe selected timing engine samples bits of the data field of the CANdata frame.

In an embodiment, the bit manipulation module is further configured tomodify at least some of the sampled bits of the data field using thesample clock frequency of the selected timing engine.

In an embodiment, the timing engine resolver is further configured toselect a best timing engine and at least one candidate timing engine.

In an embodiment, the best timing engine and the at least one candidatetiming engine sample the same data from the received bits of thearbitration field.

In an embodiment, the best timing engine has the lowest timing erroramong the best timing engine and the at least one candidate timingengine.

In an embodiment, the timing engine resolver is further configured toevaluate the best timing engine and the at least one candidate timingengine based on the subsequent bits of the CAN data frame.

In an embodiment, the timing engine resolver is further configured toselect a second timing engine with the lowest timing error among thebest timing engine and the at least one candidate timing engine. Thesecond timing engine samples further bits of the CAN data frame that arereceived after the subsequent bits of the CAN data frame.

In an embodiment, a non-transitory computer-readable storage mediumcontains program instructions for operating a CAN device. Execution ofthe program instructions by one or more processors of the computersystem causes the one or more processors to perform steps comprising inresponse to receiving bits of an arbitration field of a CAN data frameat the CAN device, selecting a timing engine from a plurality of timingengines and sampling subsequent bits of the CAN data frame using theselected timing engine. The timing engines have different sample clockfrequencies.

In an embodiment, the steps further comprise modifying at least some ofthe sampled subsequent bits of the CAN data frame using the sample clockfrequency of the selected timing engine.

Other aspects in accordance with the invention will become apparent fromthe following detailed description, taken in conjunction with theaccompanying drawings, illustrated by way of example of the principlesof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a CAN network that includes multiple CAN nodes connectedto a CAN bus.

FIG. 2 depicts an expanded view of one CAN node from FIG. 1.

FIG. 3 depicts a Nominal Bit Time (NBT) defined in the CAN protocol.

FIG. 4 depicts a CAN device that uses multiple timing engines running atdifferent clock rates.

FIG. 5 illustrates an exemplary synchronization timing for the timingengines of the CAN device depicted in FIG. 4.

FIG. 6 depicts the format of a CAN data frame that is received at theCAN device depicted in FIG. 4.

FIG. 7 depicts four synchronization edges during the reception of theCAN data frame depicted in FIG. 6.

FIG. 8 depicts an example timing engine selection at the foursynchronization edges depicted in FIG. 7.

FIG. 9 depicts the CAN device depicted in FIG. 4 embodied as a packagedIC device.

FIG. 10 is a process flow diagram of a method for operating a CAN devicein accordance with an embodiment of the invention.

Throughout the description, similar reference numbers may be used toidentify similar elements.

DETAILED DESCRIPTION

It will be readily understood that the components of the embodiments asgenerally described herein and illustrated in the appended figures couldbe arranged and designed in a wide variety of different configurations.Thus, the following more detailed description of various embodiments, asrepresented in the figures, is not intended to limit the scope of thepresent disclosure, but is merely representative of various embodiments.While the various aspects of the embodiments are presented in drawings,the drawings are not necessarily drawn to scale unless specificallyindicated.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by this detailed description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

Reference throughout this specification to features, advantages, orsimilar language does not imply that all of the features and advantagesthat may be realized with the present invention should be or are in anysingle embodiment of the invention. Rather, language referring to thefeatures and advantages is understood to mean that a specific feature,advantage, or characteristic described in connection with an embodimentis included in at least one embodiment of the present invention. Thus,discussions of the features and advantages, and similar language,throughout this specification may, but do not necessarily, refer to thesame embodiment.

Furthermore, the described features, advantages, and characteristics ofthe invention may be combined in any suitable manner in one or moreembodiments. One skilled in the relevant art will recognize, in light ofthe description herein, that the invention can be practiced without oneor more of the specific features or advantages of a particularembodiment. In other instances, additional features and advantages maybe recognized in certain embodiments that may not be present in allembodiments of the invention.

Reference throughout this specification to “one embodiment”, “anembodiment”, or similar language means that a particular feature,structure, or characteristic described in connection with the indicatedembodiment is included in at least one embodiment of the presentinvention. Thus, the phrases “in one embodiment”, “in an embodiment”,and similar language throughout this specification may, but do notnecessarily, all refer to the same embodiment.

Techniques described herein can be applied to any type of in-vehiclenetworks (IVNs), including a Controller Area Network (CAN), a LocalInterconnect Network (LIN), a Media Oriented Systems Transport (MOST)network, a FlexRay™ compatible network, and other types of IVNs.Although in some embodiments a specific type of IVN is described, itshould be noted that the invention is not restricted to a specific typeof IVN.

FIG. 1 depicts a CAN network 100 that includes multiple CAN nodes 102,also referred to as “ECUs,” each connected to a CAN bus 104. In theembodiment of FIG. 1, each CAN node includes a microcontroller 110having an embedded CAN protocol controller 114 and a CAN transceiver120. The microcontrollers are typically connected to at least one device(not shown) such as a sensor, an actuator, or some other control deviceand are programmed to determine the meaning of received messages and togenerate appropriate outgoing messages. The microcontrollers, alsoreferred to as host processors, hosts, or digital signal processors(DSPs), are known in the field. In an embodiment, the host supportsapplication software that interacts with the CAN protocol controller.

The CAN protocol controllers 114, which can be embedded within themicrocontrollers 110 or external to the microcontrollers (e.g., aseparate IC device), implement data link layer operations as is known inthe field. For example, in receive operations, a CAN protocol controllerstores received serial bits from the transceiver until an entire messageis available for fetching by the microcontroller. The CAN protocolcontroller can also decode the CAN messages according to thestandardized frame format of the CAN protocol. In transmit operations,the CAN protocol controller receives messages from the microcontrollerand transmits the messages as serial bits in the CAN data frame formatto the CAN transceiver.

The CAN transceivers 120 are located between the microcontrollers 110and the CAN bus 104 and implement physical layer operations. Forexample, in receive operations, a CAN transceiver converts analogdifferential signals from the CAN bus to serial digital signals that theCAN protocol controller 114 can interpret. The CAN transceiver alsoprotects the CAN protocol controller from extreme electrical conditionson the CAN bus, e.g., electrical surges. In transmit operations, the CANtransceiver converts serial digital bits received from the CAN protocolcontroller into analog differential signals that are sent on the CANbus.

The CAN bus 104 carries analog differential signals and includes a CANhigh (CANH) bus line 124 and a CAN low (CANL) bus line 126. The CAN busis known in the field.

FIG. 2 depicts an expanded view of one CAN node 102 from FIG. 1. In theexpanded view of FIG. 2, the microcontroller includes a host 116, whichmay be, for example, a software application that is stored in memory ofthe microcontroller and executed by processing circuits of themicrocontroller. The microcontroller 110 and the CAN transceiver 120 ofthe CAN node are connected between a supply voltage, V_(CC), and ground,GND. As illustrated in FIG. 2, data communicated from themicrocontroller to the CAN transceiver is identified as transmit data(TXD) and data communicated from the CAN transceiver to themicrocontroller is referred to as receive data (RXD). Throughout thedescription, TXD is carried on a TXD path and RXD is carried on an RXDpath. Data is communicated to and from the CAN bus via the CANH and CANLbus lines 124 and 126, respectively.

As noted above, the CAN protocol controller 114 can be configured tosupport the normal mode or the flexible data rate mode. As used herein,“CAN normal mode” (also referred to as “Classical CAN mode”) refers toframes that are formatted according to the ISO 11898-1 standard and “CANFD mode” refers to frames that are formatted according to the emergingISO/Draft International Standard (DIS) 11898-1 standard, or anequivalent thereof.

In CAN devices, the internal clock base is extracted from received dataand clock synchronization can occur on negative edges of the bits. Forexample, if a long string of the same value bit, for example 1's, isreceived, there is no negative edge to allow synchronization to occur.In order to limit the number of bits received before synchronizationoccurs, the CAN protocol uses bit stuffing. The CAN bit stuffing ruleallows, at most, five consecutive bits with the same polarity, thusassuring that there are enough polarity changes in the data tosynchronize sufficiently. For example, when five bits identical bits ina row are received, a stuffing bit of the opposite value may be put intothe bit stream in order to force a transition. Under this rule, asynchronization will occur within at least every ten bits. FIG. 3depicts a Nominal Bit Time (NBT) 300 as defined in the CAN protocol. Inorder to have a finer synchronization granularity than the NBT, TimeQuantas (Tq) can be defined in a CAN bit. As depicted in FIG. 3, a CANbit 301 is divided into a synchronization (Sync) segment 302, a Propsegment 304, and Phase 1 and Phase 2 segments 306, 308, which arerelated to physical delays in CAN communications. The Sync segment maybe the part of the bit time used to synchronize the various CAN deviceson the CAN bus. A synchronization edge may be expected within thissegment. The Prop segment may be the part of the bit time used tocompensate for physical delay times within the CAN network 100. Thesedelay times may include the signal propagation time on the CAN bus andthe internal delay time of the CAN receivers. The Phase 1 and Phase 2segments may be used to compensate for edge phase errors. These segmentsmay be lengthened or shortened by resynchronization. The data samplingpoint 310 is the point of time at which the bus level is read andinterpreted as the value of that respective bit. The data sampling pointis defined as the transition from Phase 1 to Phase 2. However, in someembodiments, a CAN transceiver 120 samples on each Tq. If a data edge isreceived in another segment than the Sync segment, the CAN transceiver'sinternal time base is shifted by X Tq, to align it with the time base ofthe incoming data. The maximum time shift is defined by the Sync JumpWidth (SJW) parameter. In an embodiment, the NBT may be up to 25 Tq,while the SJW may be limited to 4 Tq.

In accordance with an embodiment of the invention, a CAN device includestiming engines having different sample clock frequencies and a timingengine resolver configured to, in response to receiving bits of anarbitration field of a CAN data frame at the CAN device, select a timingengine from the timing engines. The selected timing engine samplessubsequent bits of the CAN data frame. By selecting a timing enginebased on bits of the arbitration field of a CAN data frame and samplingsubsequent bits of the CAN data frame using the selected timing engine,a matching sampling frequency can be determined on the fly during thereception of the CAN data frame. For example, a matching samplingfrequency is a sampling frequency at which the sampled results match thereceived CAN frame data. Consequently, data modification can be made toa CAN data frame using a matching sampling frequency prior to the cyclicredundancy check (CRC) segment of the CAN data frame. For example, a CANdata frame formatted according to the CAN FD mode can be modified into aformat that is understandable by a classic CAN device and does not causethe classic CAN device to enter an error state.

FIG. 4 depicts a CAN device 440 that uses multiple timing engines 444-1,444-2, 444-3 running at different sample clock rates. The CAN devicedepicted in FIG. 4 may be an embodiment of the CAN node 102 depicted inFIGS. 1 and 2. In some embodiments, the CAN device depicted in FIG. 4 isan embodiment of the CAN transceiver 120 depicted in FIGS. 1 and 2. Inthe embodiment depicted in FIG. 4, a CAN device 440 includes a timingmodule 442 having multiple timing engines 444-1, 444-2, 444-3 and a bitmanipulation module 448. The CAN device may be connected to a CAN bus404 and receive data from other devices on a CAN network from the CANbus. The timing module may receive data bits and may detect the timinginformation of the data. The timing module may then provide the receiveddata message to the bit manipulation module for processing. In anembodiment, the timing module and the bit manipulation module areincluded in the same IC package. However, in other embodiments, thetiming module and the bit manipulation module are included in separateIC packages. Although the illustrated CAN device is shown with certaincomponents and described with certain functionality herein, otherembodiments of the CAN device may include fewer or more components toimplement the same, less, or more functionality. For example, althoughthe CAN device is shown in FIG. 3 as including three timing engines, inother embodiments, the CAN device may include two timing engines or morethan three timing engines.

In the embodiment depicted in FIG. 4, the timing module 442 includes thefirst, second, and third timing engines 444-1, 444-2, 444-3 and thetiming engine resolver 446. Each of the first, second, and third timingengines have slightly different average clock frequencies. In someembodiments, the clock frequencies of the first, second, and thirdtiming engines have small deviations with respect to a reference clockfrequency. For example, the CAN protocol may specify that a transmittingCAN protocol engine has a clock frequency with an accuracy of ±0.5%. Inthis example, the clock frequency of the timing module may have adeviation of ±1.5% with respect to a reference clock frequency, and theclock frequencies of the first, second, and third timing engines mayhave deviations of +1%, 0%, −1% with respect to the clock frequency ofthe timing module. Consequently, out of the first, second, and thirdtiming engines, there will always be a timing engine with a clockfrequency that falls within the clock frequency range for a transmittingCAN node. Each of the first, second, and third timing engines mayreceive data bits from the CAN bus 404 and may, independently and inparallel, process the received data bits. Each of the first, second, andthird timing engines may then output an indication that the receiveddata bits were successfully detected as well as a message represented bythe received data bits. The timing engine resolver may be configured todetermine which, if any, of the first, second, and third timing enginesindicate that the respective timing engine successfully detected thereceived data bits, and then provides the message to the bitmanipulation module 448.

FIG. 5 illustrates an exemplary synchronization timing for the timingengines 444-1, 444-2, 444-3 of the CAN device 440 depicted in FIG. 4.Each of the first, second, and third timing engines have an average NBTthat is related to the clock frequency of the respective timing engine.The average NBT is adapted for the second and third engines byadding/subtracting a delay 0 for M in N bits. Specifically, the firsttiming engine has a clock frequency f₁ with an average NBT. The secondtiming engine runs with an average NBT of:

$\begin{matrix}{{{\overset{\_}{NBT}}_{(2)} = \frac{{\left( {N - M} \right)*{NBT}} + {M*\left( {{NBT} + \theta} \right)}}{N}},} & (1)\end{matrix}$

which leads to a clock frequency of:

f ₂=1/NBT ₍₂₎   (2)

The third timing engine runs with an average NBT of:

$\begin{matrix}{{{\overset{\_}{NBT}}_{(3)} = \frac{{\left( {N - M} \right)*{NBT}} + {M*\left( {{NBT} - \theta} \right)}}{N}},} & (3)\end{matrix}$

which leads to a clock frequency of:

f ₃=1/NBT ₍₃₎   (4)

In the synchronization timing shown in FIG. 5, M is set to 3 and N isset to 10. Note that, for the second timing engine, NBT's are reduced by0 so that, at the end of a synch period bits, the total time differenceversus the first timing engine is M*θ. In a similar manner, for thethird timing engine, the difference is increased by M*θ.

Because the detection bandwidths of the first, second, and third timingengines 444-1, 444-2, 444-3 overlap, two (or even all) of the timingengines may indicate the successful receipt of a message. In suchinstances, the timing engine resolver 446 may select one of the twotiming engines that indicated successful receipt of a message and mayuse that timing engine to provide the message to the bit manipulationmodule 448. In some embodiments, if two different timing engines bothindicate successful receipt of a message, the timing engine resolver maythen select the timing engine with the lowest timing error.

In an example of the operation of the CAN device 440 depicted in FIG. 4,at the beginning of each CAN data frame and on each synchronizationevent, the time basis of the first, second, and third timing engines444-1, 444-2, 444-3 are restarted. During the reception of the CAN dataframe, the calculated errors are summed. The actual error SJW at asynchronization event is:

SJW(i)=N*θ  (5)

where θ is the mismatch of nominal bit time of the engine and the bittime of the incoming data, and N is the number of bits since the lastsynchronization event. The error of timing engine x (x is an integer) atsynchronization event I is:

$\begin{matrix}{{e_{x}(I)} = {\sum\limits_{i = 1}^{I}{{SJW}(i)}}} & (6)\end{matrix}$

FIG. 6 depicts the format of a CAN data frame 600 that is received atthe CAN device 440 depicted in FIG. 4. The CAN data frame depicted inFIG. 6 may be an ISO 11898-1 frame 130 (in the classical base frameformat (CBFF) or standard format) that is used in CAN normal mode or anISO/DIS 11898-1 frame 132 (in the FD base frame format or FBFF) that isused in CAN FD mode. As depicted in FIG. 6, the CAN data frame includesa Start of Frame (SOF) field/phase 602, an arbitration field/phase 604,a control field/phase 606, a data field/phase 608, a Cyclic RedundancyCheck (CRC) field/phase 610, an Acknowledgement (ACK) field/phase 612,and an End Of Frame (EOF) field/phase 614.

During the reception of the arbitration field 604 of the CAN data frame600, there can be multiple CAN nodes in the CAN network that aretransmitting their identifier (ID) on the CAN bus 404. However, due todelay in the CAN network, the dominant bits can be longer that thenominal bit time, which affects the measurement and can result in ahigher timing error value, e_(x), for the timing engines compared to anarbitration phase with a single active CAN node. It can even result inthat the best matching engine has a higher timing error e_(x) value thana less optimal engine. If the CAN data frame that is received meets alltiming requirements as stated in IS011898, the following lemma's arevalid at the end of the arbitration field 604:

-   The best timing engine (lowest θ) has not lost synchronization-   Some timing engines with higher timing error value, e_(x), than the    best timing engine, may have sampled the same data during the    arbitration field as the best engine. Consequently, it is desirable    to choose these timing engines as candidate timing engines.

After the arbitration field 604 is received at the CAN device 440, thecontrol field 606 is received at the CAN device. From the control field,until the acknowledge field, only the CAN node that has won thearbitration, is allowed to transmit. This means that during reception ofthe control field, no disturbance on the bit timing due to multiplesenders is expected.

In the control and data fields 606, 608, additions to, modifications of,and removing of the bits can be performed by the bit manipulation module448. For example, a CAN data frame formatted according to the CAN FDmode can be modified by the bit manipulation module into a format thatis understandable by a classic CAN device or that can be skipped by aclassic CAN device without entering an error state. To time theseadded/removed/modified bits, a single timing engine should be selected.Prior to the control and data field, a preselection of timing enginesmay be performed by the timing engine resolver 446. For example, thetiming engine resolver may select the timing engine with the lowesttiming error e_(x) (the best timing engine) among all of the timingengines that have sampled the same data during the arbitration field604. In addition to the best timing engine, the timing engine resolvermay also select any of the other timing engines that have sampled thesame data during the arbitration field as possible timing enginecandidates. During reception of subsequent bits of the CAN data frame, acandidate timing engine may have a lower timing error than thepreviously selected best timing engine. In this case, the candidatetiming engine is selected as the new best timing engine.

Timing engines that have a relative low timing error e_(x), but havesampled different data are considered as being not reliable and will notbe selected during the reception of the control field and the datafield. During the reception of the control field and the data field, thesummed errors of the preselected timing engines are evaluatedconcurrently or at selected moments. The selection of the timing enginefor the subsequently received bits can change during the control anddata fields, based on the timing error e_(x). For long CAN data frames,the engine with the nominal bit timing closest to the bit timing of thereceived data is selected for the acknowledge field.

A timing engine selection operation of the CAN device 440 during thereception of the CAN data frame 600 is described with reference to FIGS.7 and 8. FIG. 7 depicts four synchronization edges 702, 704, 706, 708during the reception of the CAN data frame 600 depicted in FIG. 6. Ateach synchronization edge, one or more timing engines is selected forthe CAN device. As depicted in FIG. 7, a first synchronization edge 702occurs during the arbitration field 604 and subsequent second, third andfourth synchronization edges occur during the data field 608. Thesecond, third and fourth synchronization edges 704, 706, 708 may notoccur right after the first synchronization edge. For example, one ormore intermediate synchronization edges may occur between the firstsynchronization edge and the second synchronization edge.

FIG. 8 depicts the corresponding timing engine selection at the foursynchronization edges depicted in FIG. 7. In the example shown in FIG.8, a total of nine timing engines (TE1-TE9) are used in the CAN device440. At the first synchronization edge 702, timing engine (TE3) isselected as the best timing engine and timing engines (TE4-TE7) areselected as possible timing engine candidates. The timing engines(TE4-TE7) have sampled the same data and the timing engine (TE3) has thelowest timing error among the timing engines (TE3-TE7). The timingengines (TE1-TE3, TE8, TE9) have sampled different data from the timingengines (TE4-TE7) and are no longer considered for the current CAN dataframe. The timing engine (TE3) can be used to provide clock informationfor bit manipulation of subsequent bits of the CAN data frame 600. Atthe second synchronization edge 704, the timing engine (TE4) has thelowest timing error among the timing engines (TE3-TE7). Consequently,the timing engine (TE4) is selected as the best timing engine and isused to provide clock information for possible bit manipulation ofsubsequent bits of the CAN data frame. At the third synchronization edge706, the timing engine (TE5) has the lowest timing error among thetiming engines (TE3-TE7). Consequently, the timing engine (TE5) isselected as the best timing engine and is used to provide clockinformation for possible bit manipulation of subsequent bits of the CANdata frame. At the fourth synchronization edge 708, the timing engine(TE6) has the lowest timing error among the timing engines (TE3-TE7).Consequently, the timing engine (TE6) is selected as the best timingengine and is used to provide clock information for possible bitmanipulation of subsequent bits of the CAN data frame. As illustrated inFIG. 9, the sampling clock frequency is being dynamically adjustedduring the processing if a signal CAN data frame, which allows for a CANtransceiver to adapt on the fly within a single CAN data frame. Thisenables a CAN data frame to be manipulated before being passed to acorresponding CAN protocol controller and helps to prevent the CANprotocol controller from entering an error state.

FIG. 9 depicts the CAN device 440 depicted in FIG. 4 embodied as apackaged IC device 900. As shown in FIG. 9, the packaged IC device ofthe CAN device includes 14 pins/terminals, TXD (pin 1, transmit datainput), GND (pin 2, ground), VCC (pin 3, supply voltage), RXD (pin 4,receive data output), VIO (pin 5, supply voltage for I/O level adaptor),SDO (pin 6, SPI data output), INH (pin 7, inhibit output for switchingexternal voltage regulators), SCK (pin 8, SPI clock input), WAKE (pin 9,local wake-up input), BAT (pin 10, battery supply voltage), SDI (pin 11,Serial Peripheral Interface (SPI) data input), CANL (pin 12, LOW-levelCAN voltage input/output), CANH (pin 13, HIGH-level CAN voltageinput/output), SE (pin 8, operational mode selection) and SCSN (pin 14,SPI chip select input). The packaged IC device depicted in FIG. 9 is onepossible packaged IC device of the CAN device depicted in FIG. 4.However, the packaged IC device of the CAN device depicted in FIG. 4 isnot limited to the embodiment shown in FIG. 9. For example, although thepins are shown in FIG. 9 as locating outside of the packaged IC device,in other embodiments, some or all of the pins may locate inside/withinthe packaged IC device. In another example, in embodiments where the CANdevice does not include RXD/TXD interfaces, the packaged IC device doesnot include TXD/RXD pins. In yet another example, the packaged IC devicemay include more than 14 pins to implement more I/O functions or lessthan 14 pins to implement less I/O functions. In an embodiment, thepackaged IC device includes 8 pins/terminals, TXD (pin 1), GND (pin 2),VCC (pin 3), RXD (pin 4), n.c. (pin 5, not connected), CANL (pin 6),CANH (pin 7), and STB (pin 8, Standby mode control input).

FIG. 10 is a process flow diagram of a method for operating a CAN devicein accordance with an embodiment of the invention. At block 1002, inresponse to receiving bits of an arbitration field of a CAN data frameat the CAN device, a timing engine is selected from timing engines withdifferent sample clock frequencies. At block 1004, subsequent bits ofthe CAN data frame are sampled using the selected timing engine. The CANdevice may be the same as or similar to the CAN node 102 depicted inFIGS. 1 and 2, the CAN transceiver 120 depicted in FIGS. 1 and 2, and/orto the CAN device 440 depicted in FIG. 4.

Techniques described herein can be applied to any type of In-VehicleNetworks (IVNs), including a CAN, a LIN, a MOST network, a FlexRay™compatible network, and other types of IVNs. Although in someembodiments a CAN device is described, it should be noted that theinvention is not restricted to CAN devices. In an embodiment, theabove-described techniques can be applicable to CAN, CAN-FD, and ISO11898 compliant networks. The above-described techniques can beimplemented in a CAN device such as a CAN transceiver IC device, amicrocontroller IC device, or an IC device that includes both a CANtransceiver and a microcontroller.

In an embodiment, “CAN messages” refers to CAN “data frames,” which areCAN data frames with the RTR bit set to “0” as specified in the CANprotocol. CAN “data frames” are the CAN data frames that carry payloaddata (e.g., in the DATA field) that could be used for malicious intentand thus the CAN “data frames” are important to monitor for intrusiondetection/prevention. CAN data frames with the RTR bit set to “1” arereferred to in the protocol as “remote frames” and such frames do notinclude payload data because the function of “remote frames” is simplyto request transmission of a CAN data frame with the same identifier.Remote frames with the same identifier as a corresponding CAN data framecan be transmitted by all of the other CAN nodes (e.g., all of the CANnodes other than the CAN node that is in charge of sending the DataFrame with the same identifier). Therefore, it would not make sense tostore an identifier of an outgoing CAN remote frame, and it would notmake sense to check an incoming CAN remote frame for a matchingidentifier.

In the above description, specific details of various embodiments areprovided. However, some embodiments may be practiced with less than allof these specific details. In other instances, certain methods,procedures, components, structures, and/or functions are described in nomore detail than to enable the various embodiments of the invention, forthe sake of brevity and clarity.

Although the operations of the method(s) herein are shown and describedin a particular order, the order of the operations of each method may bealtered so that certain operations may be performed in an inverse orderor so that certain operations may be performed, at least in part,concurrently with other operations. In another embodiment, instructionsor sub-operations of distinct operations may be implemented in anintermittent and/or alternating manner.

It should also be noted that at least some of the operations for themethods described herein may be implemented using software instructionsstored on a computer useable storage medium for execution by a computer.As an example, an embodiment of a computer program product includes acomputer useable storage medium to store a computer readable program.

The computer-useable or computer-readable storage medium can be anelectronic, magnetic, optical, electromagnetic, infrared, orsemiconductor system (or apparatus or device). Examples ofnon-transitory computer-useable and computer-readable storage mediainclude a semiconductor or solid state memory, magnetic tape, aremovable computer diskette, a random access memory (RAM), a read-onlymemory (ROM), a rigid magnetic disk, and an optical disk. Currentexamples of optical disks include a compact disk with read only memory(CD-ROM), a compact disk with read/write (CD-R/W), and a digital videodisk (DVD).

Alternatively, embodiments of the invention may be implemented entirelyin hardware or in an implementation containing both hardware andsoftware elements. In embodiments which use software, the software mayinclude but is not limited to firmware, resident software, microcode,etc.

Although specific embodiments of the invention have been described andillustrated, the invention is not to be limited to the specific forms orarrangements of parts so described and illustrated. The scope of theinvention is to be defined by the claims appended hereto and theirequivalents.

What is claimed is:
 1. A method for operating a Controller Area Network(CAN) device, the method comprising: in response to receiving bits of anarbitration field of a CAN data frame at the CAN device, selecting atiming engine from a plurality of timing engines, wherein the timingengines have different sample clock frequencies; and sampling subsequentbits of the CAN data frame using the selected timing engine.
 2. Themethod of claim 1, further comprising modifying at least some of sampledsubsequent bits of the CAN data frame using the sample clock frequencyof the selected timing engine.
 3. The method of claim 2, wherein the CANdata frame further comprises a data field, and wherein sampling thesubsequent bits of the CAN data frame using the selected timing enginecomprises sampling bits of the data field of the CAN data frame usingthe selected timing engine.
 4. The method of claim 3, wherein modifyingthe at least some of the sampled subsequent bits of the CAN data framecomprises modifying at least some of the sampled bits of the data fieldusing the sample clock frequency of the selected timing engine.
 5. Themethod of claim 1, wherein selecting a timing engine comprises selectinga best timing engine and at least one candidate timing engine.
 6. Themethod of claim 5, wherein the best timing engine and the at least onecandidate timing engine sample the same data from the received bits ofthe arbitration field.
 7. The method of claim 6, wherein the best timingengine exhibits the lowest timing error among the best timing engine andthe at least one candidate timing engine.
 8. The method of claim 5,further comprising evaluating the best timing engine and the at leastone candidate timing engine based on the subsequent bits of the CAN dataframe.
 9. The method of claim 8, wherein evaluating the best timingengine and the at least one candidate timing engine based on thesubsequent bits of the CAN data frame comprises selecting a secondtiming engine with the lowest timing error among the best timing engineand the at least one candidate timing engine, and wherein the methodfurther comprises sampling further bits of the CAN data frame that arereceived after the subsequent bits of the CAN data frame using thesecond timing engine.
 10. A Controller Area Network (CAN) device, theCAN device comprising: a plurality of timing engines, wherein the timingengines have different sample clock frequencies; and a timing engineresolver configured to, in response to receiving bits of an arbitrationfield of a CAN data frame at the CAN device, select a timing engine fromthe plurality of timing engines, wherein the selected timing enginesamples subsequent bits of the CAN data frame.
 11. The CAN device ofclaim 10, further comprising a bit manipulation module configured tomodify at least some of sampled subsequent bits of the CAN data frameusing the sample clock frequency of the selected timing engine.
 12. TheCAN device of claim 11, wherein the CAN data frame further comprises adata field, and wherein the selected timing engine samples bits of thedata field of the CAN data frame.
 13. The CAN device of claim 12,wherein the bit manipulation module is further configured to modify atleast some of the sampled bits of the data field using the sample clockfrequency of the selected timing engine.
 14. The CAN device of claim 10,wherein the timing engine resolver is further configured to select abest timing engine and at least one candidate timing engine.
 15. The CANdevice of claim 14, wherein the best timing engine and the at least onecandidate timing engine sample the same data from the received bits ofthe arbitration field.
 16. The CAN device of claim 15, wherein the besttiming engine has the lowest timing error among the best timing engineand the at least one candidate timing engine.
 17. The CAN device ofclaim 16, wherein the timing engine resolver is further configured toevaluate the best timing engine and the at least one candidate timingengine based on the subsequent bits of the CAN data frame.
 18. The CANdevice of claim 17, wherein the timing engine resolver is furtherconfigured to select a second timing engine with the lowest timing erroramong the best timing engine and the at least one candidate timingengine, and wherein the second timing engine samples further bits of theCAN data frame that are received after the subsequent bits of the CANdata frame.
 19. A non-transitory computer-readable storage mediumcontaining program instructions for operating a Controller Area Network(CAN) device, wherein execution of the program instructions by one ormore processors of the computer system causes the one or more processorsto perform steps comprising: in response to receiving bits of anarbitration field of a CAN data frame at the CAN device, selecting atiming engine from a plurality of timing engines, wherein the timingengines have different sample clock frequencies; and sampling subsequentbits of the CAN data frame using the selected timing engine.
 20. Thenon-transitory computer-readable storage medium of claim 19, the stepsfurther comprising modifying at least some of the sampled subsequentbits of the CAN data frame using the sample clock frequency of theselected timing engine.